BECKHOFF BK7300 User Manual
MODBUS BK7300
Version: 1.2
Date: 2012-09-28
Table of Contents
Table of Contents
1. Foreword 1
Notes on the documentation 1
Disclaimer 1
Trademarks 1
Patent Pending 1
Copyright 1
Delivery conditions 1
Safety Instructions 2
State at Delivery 2
Description of safety symbols 2
2. Basic information 3
The Beckhoff bus terminal system 3
The interfaces 5
Power supply 5
Power supply to the power contacts 5
Power contacts 5
Fieldbus connection 5
Configuration Interface 6
KS2000 Software 6
K-bus contacts 6
Supply isolation 6
The operating modes of the bus coupler 7
Mechanical construction 8
Electrical data 10
The peripheral data in the process image 10
Preparing for Operation and Diagnostics 12
Fieldbus errors 14
BK7300
Table of Contents
3. MODBUS 15
Basic Principles 15
Bus Topology 15
Process Data and Memory Map 16
Settings and Parameterization 17
Parameterization Table 18
Protocol 19
ASCII 19
RTU 19
Functions 19
Read Digital Outputs (Function 1) 20
Read Digital Inputs (Function 2) 21
Read Analogue Outputs (Function 3) 22
Read Analogue Inputs (Function 4) 23
Writing a Digital Output (Function 5) 24
Writing an Analogue Output (Function 6) 25
Writing a Number of Digital Outputs (Function 15) 26
Writing a Number of Analogue Outputs (Function 16) 27
Writing and Reading a Number of Analogue Outputs or Inputs (Function 23) 28
Diagnostics 29
Echoes a query (Sub-Function 0) 29
Coupler Reset (Sub-Function 1) 30
Delete All Counter Contents (Sub-Function 10) 30
Bus Communication Error Counter (Sub-Function 11) 30
Error Answer Counter (Sub-Function 13) 30
Slave Answers (Sub-function 14) 30
Unsent Slave Answers (Sub-Function 15) 30
Number of Error Answers (Sub-Function 16) 30
BK7300 Error Answers 31
4. Appendix 32
MODBUS Interface 32
Terminal Mapping 34
List of References 34
5. Index 35
6. Support and Service 36
Beckhoff's branch offices and representatives 36
Beckhoff Headquarters 36
BK7300
Foreword
Foreword
Notes on the documentation
This description is only intended for the use of trained specialists in control and automation technology
who are familiar with the applicable national standards. It is essential that the following notes and
explanations are followed when installing and commissioning these components.
The responsible staff must ensure that the application or use of the products describe d satisfy all the
requirements for safety, including all the relevant laws, regulations, guidelines and standards.
Disclaimer
The documentation has been prepared with care. The products described are, however, constantly under
development. For that reason the documentation is not in every case checked for consistency with
performance data, standards or other characteristics.
In the event that it contains technical or editorial errors, we retain the right to make alterations at any time
and without warning.
No claims for the modification of products that have already been supplied may be made on the basis of
the data, diagrams and descriptions in this documentation.
Trademarks
Beckhoff®, TwinCAT®, EtherCAT®, Safety over EtherCAT®, TwinSAFE® and XFC® are registered
trademarks of and licensed by Beckhoff Automation GmbH.
Other designations used in this publication may be trademarks whose use by third parties for their own
purposes could violate the rights of the owners.
Patent Pending
The EtherCAT Technology is covered, including but not limited to the following patent applications and
patents: EP1590927, EP1789857, DE102004044764, DE102007017835 with corresponding applications
or registrations in various other countries.
The TwinCAT Technology is covered, including but not limited to the following patent applications and
patents: EP0851348, US6167425 with corresponding applications or registrations in various other
countries.
Copyright
©
Beckhoff Automation GmbH.
The reproduction, distribution and utilization of this document as well as the communication of its contents
to others without express authorization are prohibited. Offenders will be held liable for the payment of
damages. All rights reserved in the event of the grant of a patent, utility model or design.
Delivery conditions
In addition, the general delivery conditions of the company Beckhoff Automation GmbH apply.
BK7300 1
Foreword
Safety Instructions
State at Delivery
All the components are supplied in particular hardware and software configurations appropriate for the
application. Modifications to hardware or software configurations other than those described in the
documentation are not permitted, and nullify the liability of Beckhoff Automation GmbH.
Description of safety symbols
The following safety symbols are used in this operating manual. They are intended to alert the reader to
the associated safety instructions.
Serious risk of injury!
DANGER
WARNING
CAUTION
Warning
Note
Failure to follow the safety instructions associated with this symbol directly endangers
the life and health of persons.
Caution – Risk of injury!
Failure to follow the safety instructions associated with this symbol endangers the life
and health of persons.
Personal injuries!
Failure to follow the safety instructions associated with this symbol can lead to injuries
to persons.
Damage to the environment or devices
Failure to follow the instructions associated with this symbol can lead to damage to the
environment or equipment.
Tip or pointer
This symbol indicates information that contributes to better understanding.
2 BK7300
Basic information
Basic information
Up to 64 bus terminals
each with 2 I/O channels
for any form of signal
Decentralized wiring of the
I/O level
IPC as control unit
Bus couplers for all current
bus systems
Standard C rail assembly
Modularity
Display of channel status
The K-bus
End terminal
The Beckhoff bus terminal system
The bus terminal system is the universal connecting link between a
fieldbus system and the sensor/actor level. A unit consists of a bus coupler,
which is the interface to the fieldbus, and up to 64 electronic terminals, of
which the last is an end terminal. Terminals, each with two I/O channels,
are available for any form of technical signal and can be combined as
desired. The various types of terminal are all constructed in the same way,
so that the planning costs are kept extremely low. The height and depth of
the construction are calculated for compact terminal cabinets.
Fieldbus technology makes it possible to use compact control
architectures. The I/O level does not need to be taken right up to the
control unit. Sensors and actors can be connected decentrally with minimal
lengths of cable. You can position the control unit at any convenient
location in the installation. Using an industrial PC as control unit makes it
possible to implement the operating and monitoring element as part of the
control hardware, so the control unit can be located on an operating desk,
control point or similar. The bus terminals constitute the decentralized
input/output level of the control unit in the switch cabinet and its
subordinate terminal cabinets. As well as the sensor/actor level, the power
unit of the equipment is also controlled via the bus system. The bus
terminal replaces a conventional terminal as the cabling level in the switch
cabinet; the switch cabinet can be made smaller.
The Beckhoff bus terminal system combines the advantages of a bus
system with the functionality of compact terminals. Bus terminals can be
used on all current bus systems and serve to reduce the diversity of parts
in the control unit, while behaving like the conventional standard units for
the relevant bus system and supporting the entire range of functionality of
the bus system.
The simple and compact assembly on a standard C rail, and the direct
cabling of actors and sensors without cross connections between the
terminals, serve to standardize the installation, as does the uniformly
designed labeling.
The small size and great flexibility of the bus terminal system mean that
you can use it anywhere that you could use a terminal and use any type of
connection – analog, digital, serial or direct sensors.
The modular construction of the terminal row, using bus terminals with
various functions, limits the number of unused channels to at most one per
function. Two channels to a terminal is the optimum solution for the number
of unused channels and the cost per channel. The possibility of using
power input terminals to provide separate power supplies also helps to
minimize the number of unused channels.
The integrated light-emitting diodes close to the sensor/actor indicate the
status of each channel.
The K-bus is the path taken by data within the terminal row. The bus
coupler carries the K bus through all the terminals by means of six contacts
on the side walls of the terminals, and the end terminal terminates the K
bus. The user does not need to know anything about the function of the K
bus or the internal operation of terminals and bus couplers. There are
numerous software tools available which provide for convenient planning,
configuration and operation.
BK7300 3
Basic information
l
Power input terminals
for separately powered
groups
Three power contacts pass the operating power to the following terminals.
You can use power input terminals to subdivide the terminal row as desired
into groups, each with a separate power supply. These power input
terminals are not taken into account for addressing the terminals, you can
insert them at any position along the terminal row.
You can install up to 64 terminals on a terminal row, including power input
terminals and the end terminal.
The principle of the bus
terminal
Bus coupler
Bk7300
Power supp
for the
bus coupler
y
Potential
input
terminal
Bus end
terminal
K-Bus
Bus couplers for various
fieldbus systems
WD
RX
TX
ERROR
F
F
O
H
K
C
E
B
0201
24V
0V
++
PE
PE
Power
contacts
Potential
isolation
MODBUS
0
1
9
2
8
3
7
4
6
5
0
1
9
2
8
3
7
4
6
5
You can use a variety of bus couplers to attach the electronic terminal row
quickly and easily to the various fieldbus systems, and you can also
subsequently convert to a different fieldbus system. The bus coupler deals
with all the necessary monitoring and control tasks for operating the
attached bus terminals, indeed all the operation and configuration of the
bus terminals is carried out via the bus coupler. The fieldbus, K bus and I/O
level are electrically isolated.
If the exchange of data across the fieldbus is temporarily interrupted, logic
states are preserved, digital outputs are cleared and analog outputs revert
to a reset value which can be individually configured for each output when
the equipment is set up.
4 BK7300
Basic information
The interfaces
There are six ways of making a connection to a bus coupler. These
interfaces are designed as plug connections and spring terminals.
BK 7300
24V
++
PE PE
0201
Power LEDs
Bus coupler / power contacts
0V
K-Bus
Power supply bus coupler
24 V DC / GND
Input
power contacts
power contacts
The MODBUS - coupler
BK7300
MODBUS
Configuration
interface
MODBUS
WD
RX
TX
ERROR
0
1
9
2
8
3
7
4
6
5
BECKHOFF
0
1
9
2
8
3
7
4
6
5
24 V DC on the topmost
terminals
Power supply
The bus couplers need an operating power of 24 VDC which is connected
via the topmost spring terminals, labeled "24 V” and "0 V”. This power
supply serves not only the electronic components of the bus coupler but
(via the K bus) also the bus terminals. The power supply of the bus coupler
circuitry and that of the K-bus (Terminal bus) are electrically isolated from
the voltage of the field level.
Lower 3 terminal pairs for
power input
maximum 24 V
maximum 10 A
Power supply to the power contacts
The six lower connections with spring terminals can be used to supply
power to the peripherals. The spring terminals are connected in pairs to the
power contacts. The power supply to the power contacts has no
connection to the power supply of the bus couplers. The power input is
designed to permit voltages up to 24 V. The pair-wise arrangement and the
electrical connection between the feed terminal contacts makes it possible
to loop through the wires connecting to different terminal points. The load
on the power contact may not continuously exceed 10 A. The current
capacity between two spring terminals is the same as the capacity of the
connecting wires.
Spring contacts at the side
Power contacts
On the right-hand side face of the bus coupler are three spring contacts
which are the power connections. The spring contacts are recesse d in slots
to prevent them from being touched. When a bus terminal is connected,
the blade contacts on the left-hand side of the bus terminal are connected
to the spring contacts. The slot and key guides at the top and bottom of the
bus couplers and bus terminals ensure reliable location of the power
contacts.
Fieldbus connection
9 pin sub-D socket strip There is a recessed front face on the left hand side. The MODBUS
connection plug can be inserted here. A full description of the fieldbus
interfaces is found elsewhere in this manual. (In the section on The
Medium: Plugs and Cables)
BK7300 5
Basic information
Serial interface under the
front cover
6 contacts at the side
3 supply groups:
fieldbus
K-bus
peripheral level
Setting up the power levels
in the bus terminal system
Configuration Interface
The standard bus couplers have an RS232 interface at the bottom of the
front face. The miniature connector can be joined to a PC with the aid of a
connecting cable and the KS2000 configuration software. The interface
allows the analogue channels to be configured. The functionality of the
configuration interface can also be reached via the fieldbus using the PLC
interface.
KS2000 Software
In order to link the MODBUS BK7300 coupler and the KS2000
configuration software, the coupler's address selection switch must be set
to "00", and it must be restarted (i.e. the coupler must be switched off and
then on again).
K-bus contacts
The connections between the bus coupler and the bus terminals are
effected by gold contacts at the right-hand side of the bus coupler. When
the bus terminals are plugged together, these gold contacts automatically
complete the connection to the bus terminals. The K bus is responsible for
the power supply to the electronic components of the K bus in the bus
terminals, and for the exchange of data between the bus coupler and the
bus terminals. Part of the data exchange takes place via a ring structure
within the K bus. Disengaging the K bus, for example by pulling on one the
bus terminals, will break this circuit so that data can no longer be
exchanged. However, there are mechanisms in place which enable the bus
coupler to locate the interruption and report it.
Supply isolation
The bus couplers operate with three independent supplies. The input
power supplies the electrically isolated K-bus circuitry in the bus coupler
and the K-bus itself. The power supply is also used to generate the
operating power for the fieldbus.
Note: All the bus terminals are electrically isolated from the K bus, so that
the K-bus is completely electrically isolated.
Bus terminalsBus coupler
Terminal bus
Field bus
Periphery level
24 V DC
6 BK7300
Basic information
When it is first switched on the bus coupler carries out a self-test to check
Start-up behavior of the bus
coupler
The operating modes of the bus coupler
the functions of its components and the communications of the K bus, and
while this is going on the red I/O LED will flash. When the self-test has
been completed successfully, the bus coupler will begin to test the
attached bus terminals (the "bus terminal test”) and read in the
configuration from which it constructs an internal structure list, which is not
accessible from outside. If an error occurs the bus coupler will enter the
operating mode "STOP”. If the start-up sequence is completed without
errors the bus coupler will enter the mode "fieldbus start”.
Power on selftest
Bus terminal test
Structure list
OK
Field bus start
Error
Stop
BK7300 7
Basic information
Mechanical construction
The Beckhoff bus terminal system is remarkable for its compact
construction and high degree of modularity. When you design the
installation you will need to plan for one bus coupler and some number of
bus terminals. The dimensions of the bus couplers do not depend on the
fieldbus system. If you use large plugs, for example like some of the bus
plugs used for the PROFIBUS, they may protrude above the overall height
of the cabinet.
Dimensions of a bus
coupler
MODBUS
RUN
RX
TX
Error
01
24V
02
0V
01
24V
02
0V
12
+
PE
100
94
+++
0
1
9
2
8
3
7
4
6
5
BECKHOFF
BK 7300
PEPEPE
0
1
9
2
8
3
7
4
6
5
47
The overall width of the construction is the width of the bus coupler,
including the bus end terminal, plus the width of the installed bus terminals.
The bus terminals are 12 mm or 24 mm wide, depending on their function.
Depending on the gauge of cables used the overall height of 68 mm may
be overstepped by about 5 mm to 10 mm by the cables at the front.
Assembly and connections It takes only a slight pressure to latch the bus coupler and the various bus
terminals onto a supporting 35 mm rail and a locking mechanism then
prevents the individual housings from being removed. You can remove
them without effort if you first release the latching mechanism by pulling the
orange tab. You should carry out work on the bus terminals and the bus
coupler only while they are switched off: if you plug or unplug components
while the power is on you may briefly provoke some undefined state (and,
for instance, reset the bus coupler).
Maximum number of
terminals
You can attach up to 64 bus terminals in series on the right-hand side of
the bus coupler. When you assemble the components, make sure that you
mount the housings so that each slot comes together with the
corresponding key. You cannot make any functional connections merely by
pushing the housings together along the supporting track. When they are
correctly mounted there should be no appreciable gap between the
adjacent housings.
8 BK7300
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